Spectroscopy

Question 1

What is spectroscopy?

Answer 1

measures the energy differences between the possible states of a molecular system by determining the frequencies of electromagnetic radiation absorbed by the molecules

Question 2

What is the fingerprint region range?

Answer 2

1500 and 400 cm-1

Question 3

What is the range/shape for hydroxyls on alcohols?

Answer 3

3300 cm-1; broad wide peak

Question 4

What is the range/shape for hydroxyls on carboxylic acids?

Answer 4

3000 cm-1; broad wide peak

Question 5

What is the range/shape for carbonyl?

Answer 5

1700 cm-1; sharp, deep peak

Question 6

What is the range/shape for N-H bonds?

Answer 6

3300 cm-1; sharp peak

Question 7

What is the range for IR spectrum?

Answer 7

1400 and 4000 cm-1

Question 8

What does IR spectroscopy measure?

Answer 8

molecular vibrations

Question 9

How is UV spectroscopy performed?

Answer 9

passing UV light through a sample that is usually dissolved in an inert, nonabsorbing solvent and recording the absorbance

Question 10

What information does UV spectroscopy give us?

Answer 10

wavelength of maximum absorbance which tells the extend of the conjugation in the conjugated systems; greater wavelength means more conjugated

Question 11

What are conjugated molecules?

Answer 11

molecules with unhybridized p orbitals

Question 12

What is NMR based on?

Answer 12

certain atomic nuclei have magnetic moments that are oriented at random

Question 13

What does NMR plot?

Answer 13

frequency vs absorption of energy

Question 14

What is used as a calibration for NMR?

Answer 14

tetramethylsilane (TMS)

Question 15

What does the number of peaks on NMR tell you?

Answer 15

for each peaks section, use n + 1. If the proton has n protons that are three bonds away it will result in n+1 peaks

Question 16

What is the coupling constant (J)?

Answer 16

magnitude of splitting

Question 17

NMR range for sp3-hybridized carbons

Answer 17

0 - 3.0 ppm

Question 18

NMR range for sp2-hybridized carbons

Answer 18

4.6 - 6.0 ppm

Question 19

NMR range for sp-hybridized carbons

Answer 19

2.0 - 3.0 ppm

Question 20

NMR range for alkyl group

Answer 20

0 to 3 ppm

Question 21

NMR range for alkynes

Answer 21

2 to 3 ppm

Question 22

NMR range for alkenes

Answer 22

4.6 to 6 ppm

Question 23

NMR range for aromatics

Answer 23

6 to 8.5 ppm

Question 24

NMR range for aldehydes

Answer 24

9 to 10 ppm

Question 25

NMR range for carboxylic acids

Answer 25

10.5 to 12 ppm

Question 26

What is spin spin coupling?

Answer 26

occurs when two protons close to one another have an effect on the other’s magnetic environment

Question 27

What is the effect of deshielding?

Answer 27

deshielding occurs in molecules that have electronegative atoms and pull electron density away from the hydrogens being measured; results in downfield shift of the proton peak